Biological Mineralization Research Articles

Crystallization of smooth amorphous calcium phosphate microspheres to core-shell hydroxyapatite microspheres.

Calcium phosphates (Ca-P) represent a significant class of biological minerals found in natural hard tissues. Crystallization through phase transformation of a metastable precursor is an effective strategy to guide the growth of crystalline Ca-P with exceptional functionality. Despite extensive research on Ca-P, the exact process during the crystallization of amorphous particles to hydroxyapatite (HA) remains elusive. Herein, pure HA microspheres with a core-shell structure are crystallized via dissolution and re-crystallization of smooth amorphous calcium phosphate (ACP) microspheres. The transformation is initiated with the increase of the hydrothermal treatment time in the presence of sodium trimetaphosphate and l-glutamic. The underlying mechanisms along with the kinetics of such transformation are explored. Nanocrystalline areas are formed on the smooth ACP microspheres and crystallization advances via nanometre-sized clusters formed by directional arrangement of nanocrystalline whiskers. Our findings shed light on a crucial but unclear stage in the genesis of HA crystals, specifically under the conditions of hydrothermal synthesis.

Biomimetic Remineralization of Dental Hard Tissues via Amyloid‐Like Protein Matrix Composite with Amorphous Calcium Phosphate

AbstractNumerous remineralizing coatings aim to prevent or treat early enamel lesions and occlude exposed dentinal tubules (DTs). Nevertheless, the pace of remineralization is inadequate, and the mechanical robustness of the newly established mineral layer fails to match the inherent strength. In this study, a biomimetic mineralization strategy aimed at replicating key events in biological mineralization, specifically focusing on the organic–inorganic composite matrix, is proposed. The material utilizes Tris(2‐carboxyethyl)phosphine (TCEP), which serves a dual role: stabilized amorphous calcium phosphate (ACP) (ACP@TCEP) nanoparticles as its inorganic component, and catalyzing the cleavage of intramolecular disulfide bonds in poly(ethylene glycol) (PEG) grafted lysozyme (lyso‐PEG) to facilitate the formation of an amyloid‐like protein matrix composite with ACP (ACP@lyso‐PEG nanocomplexes). ACP@lyso‐PEG nanocomplexes can rapidly and efficiently form an enamel‐like remineralization layer on the surface of damaged dental hard tissue, reaching ≈4.205 µm thickness after 3 days of acid‐etched enamel. Furthermore, achieving a depth of DTs occlusion exceeding 60 µm after 5 days, using a simple immersion process. The resulting mineralized layer exhibits mechanical strength comparable to natural teeth. This study introduces a conceptual biomimetic mineralization strategy for effective enamel repair or DTs occlusion in clinical practices, and offers potential insights into the mechanisms of biomineral formation.

Effects of small-scale topography on organic sulfur mineralization of subtropical soils

Organic sulfur (S) mineralization is an important source of sulfate in soils, compared to atmospheric and weathering inputs. Previous studies on the effects of topography on the decomposition of organic matter have focused exclusively on mountainous regions with steep slopes, without considering low hilly regions with gentle slopes. It therefore remains unclear whether and how hilly regions create distinct environmental conditions that could affect organic S mineralization. We determined S sources, speciation and decomposition index in soil profiles and corresponding plant samples along a catena in a subtropical monsoon climate using a combination of S isotope ratios and S K-edge X-ray absorption near edge structure (XANES) spectroscopy. Sulfur in surface soils is mainly derived from decomposing litter. The decomposition of organic S is the primary process influencing the proportions of water-soluble and adsorbed SO42− in soil profiles. Pedogenic Fe and Al minerals contribute significantly to S stabilization in soils. The most oxidized S species are abundant in plants (10–56%) and may have the potential to stimulate biochemical mineralization through the hydrolysis of ester-S, thereby enhancing S-supplying capacity of soils. Water availability, influenced by small-scale topography, plays a key role in the S biological mineralization. The slower S decomposition rates at the lower elevation can be attributed to the high water content that inhibits microbial activities. Our results suggest that incorporating local-scale topography into the modeling frameworks may improve predictions of ecosystem S status and its responses to climate change.

Citrate Improves Biomimetic Mineralization Induced by Polyelectrolyte-Cation Complexes Using PAsp-Ca&Mg Complexes.

Magnesium ions are highly enriched in early stage of biological mineralization of hard tissues. Paradoxically, hydroxyapatite (HAp) crystallization is inhibited significantly by high concentration of magnesium ions. The mechanism to regulate magnesium-doped biomimetic mineralization of collagen fibrils has never been fully elucidated. Herein, it is revealed that citrate can bioinspire the magnesium-stabilized mineral precursors to generate magnesium-doped biomimetic mineralization as follows: Citrate can enhance the electronegativity of collagen fibrils by its absorption to fibrils via hydrogen bonds. Afterward, electronegative collagen fibrils can attract highly concentrated electropositive polyaspartic acid-Ca&Mg (PAsp-Ca&Mg) complexes followed by phosphate solution via strong electrostatic attraction. Meanwhile, citrate adsorbed in/on fibrils can eliminate mineralization inhibitory effects of magnesium ions by breaking hydration layer surrounding magnesium ions and thus reduce dehydration energy barrier for rapid fulfillment of biomimetic mineralization. The remineralized demineralized dentin with magnesium-doped HAp possesses antibacterial ability, and the mineralization mediums possess excellent biocompatibility via cytotoxicity and oral mucosa irritation tests. This strategy shall shed light on cationic ions-doped biomimetic mineralization with antibacterial ability via modifying collagen fibrils and eliminating mineralization inhibitory effects of some cationic ions, as well as can excite attention to the neglected multiple regulations of small biomolecules, such as citrate, during biomineralization process.

Altered soil nitrogen retention by grassland acidification from near-neutral to acidic conditions: A plant-soil-microbe perspective

Grassland ecosystems are facing soil acidification, occurring either rapidly or gradually, alongside the persistent threats of acid deposition and nitrogen (N) pollution. However, the understanding of how grassland soils retain N in response to acidification remains limited, despite its critical importance in providing essential services in these ecosystems. Considering the prevalence of near-neutral or weak-acidic (e.g., pH 6) soils in grasslands worldwide, we aim to predict the pathways through which grassland acidification alters soil N retention. Firstly, as soil fungal proportions increase, the carbon:nitrogen ratios of the microbial community also rise, leading to a downregulation of microbial N uptake and retention. Secondly, grassland acidification weakens the stability of soil organic matter (SOM) by physically and chemically dissolving its components, but also conserves SOM by hindering biological mineralization, thereby enhancing N retention. Thirdly, acidification damages 2:1 clay minerals and causes occupation of exchangeable positions by H+, liberating fixed ammonium and subsequently attenuating grassland soil N retention. Fourthly, acidification leads to the breakup of macroaggregates, exposing SOM to microbial attack but also compromising microbial habitats and activity, resulting in uncertainty in grassland N retention. Fifthly, dominant plant stress-tolerators allocate more N aboveground as less decomposable defensive metabolites, reducing the risk of N loss during grassland litter degradation. Overall, in future research, it is crucial to focus on anticipating the changes in soil N retention under acidification, highlighting the synergistic or antagonistic interactions among the reviewed grassland modulators/processes, and quantifying the impacts of declined N deposition on grassland soil N retention and cycling, given the current and recent past stable or even declined atmospheric N deposition in many regions.

Analysis of multiyear seasonal spatial-temporal chlorophyll-a concentration dynamics in the coastal zone of north-western of the Sea of Japan

The coastal zone and shelf of the north-western of the Sea of Japan have high biological productivity. The vegetation of microalgae is realized due to insolation, nutrient input with river runoff and as a result of seasonal vertical mixing of water masses. Also, the productivity activity relates to the type of marine landscape. Phytoplankton assemblages are first-order food resources for zooplankton and the second for nekton (fish, mammals), and they also serve as a source of biological minerals from the decayed of their dead cell products, which as suspended particles (detritus) provide food for pelagic bacteria and bottom biocenoses. The vertical subdivision of the landscape - neritho-pelagial (coastal zone) of the studied part of the sea reflects a wide biological diversity represented by bottom communities of living organisms. The research objective of this article studied to analyze the spatial and temporal dynamics of chlorophyll-a concentration in phytoplankton in different landscape-bionomic areas in the north- western of the Sea of Japan for each season from 2003 to 2022’s. The article is used the landscape-bionomic and space monitoring data approaches. The known system of units of global zoning of ecoregions (sea basins) describes the natural features of the sea. The fundamental unit of regional zoning is coastal morphostructures or marine landscape which builds ecological conditions for hydrobionts. Space monitoring from the Aqua satellite, NASA, covers the upper layers of water at a wide resolution. Water surface temperature and chlorophyll-a concentration for 20 years (2003-2022's) are compared on the basis of satellite data. Practical significance: the paper discloses the links between landscape-bionomic areas and seasonal multiyear dynamics of temperature and phytoplankton productivity in the north- western of the Sea of Japan. The comprehensive approach will serve as a necessity for the rational use of aquatic biological resources. Moreover, satellite data can be applied to the construction of long-term forecasts of climate variability in the region.

Mathematical model of physicochemical regulation of precipitation of bone hydroxyapatite

IntroductionFormation of hydroxyapatite in bone, dentin, and enamel occurs at restricted molecular sites of specific extracellular matrix proteins and is controlled by multiple mineralization inhibitors. However, the role of physicochemical factors, such as the availability of required ions and the saturation status of the aqueous environment in biological mineralization, is not fully understood. The goal of this study was to use mathematical modeling to describe the complex physicochemical environment permissive to the precipitation of biological hydroxyapatite.MethodsWe simulated the processes occurring in the bone interstitial fluid (ISF) defined as an aqueous environment containing seven chemical components (calcium, phosphate, carbonate, sodium, potassium, magnesium, and chloride) that form 30 chemical species. We simulated reversible equilibrium reactions among these chemical species, and calculated supersaturation for hydroxyapatite and its precipitation rate using kinetic theory.Results and DiscussionThe simulated ISF was of correct ionic strength and predicted the equilibrium component concentrations that were consistent with the experimental findings. Supersaturation of physiological ISF was ~15, which is consistent with prior findings that mineralization inhibitors are required to prevent spontaneous mineral precipitation. Only total calcium, total phosphate and to a lesser degree total carbonate affected ion availability, solution supersaturation and hydroxyapatite precipitation rate. Both calcium and phosphate levels directly affected hydroxyapatite precipitation, and phosphate was affected by pH, which additionally influenced hydroxyapatite precipitation. Integrating mathematical models capturing the physiochemical and biological factors regulating bone mineralization will allow in silico studies of complex clinical scenarios associated with alterations in ISF ion composition, such as rickets, hypophosphatemia, and chronic kidney disease.

Towards Polycaprolactone-Based Scaffolds for Alveolar Bone Tissue Engineering: A Biomimetic Approach in a 3D Printing Technique.

The alveolar bone is a unique type of bone, and the goal of bone tissue engineering (BTE) is to develop methods to facilitate its regeneration. Currently, an emerging trend involves the fabrication of polycaprolactone (PCL)-based scaffolds using a three-dimensional (3D) printing technique to enhance an osteoconductive architecture. These scaffolds are further modified with hydroxyapatite (HA), type I collagen (CGI), or chitosan (CS) to impart high osteoinductive potential. In conjunction with cell therapy, these scaffolds may serve as an appealing alternative to bone autografts. This review discusses research gaps in the designing of 3D-printed PCL-based scaffolds from a biomimetic perspective. The article begins with a systematic analysis of biological mineralisation (biomineralisation) and ossification to optimise the scaffold's structural, mechanical, degradation, and surface properties. This scaffold-designing strategy lays the groundwork for developing a research pathway that spans fundamental principles such as molecular dynamics (MD) simulations and fabrication techniques. Ultimately, this paves the way for systematic in vitro and in vivo studies, leading to potential clinical applications.

Electrochemical In Situ Hydrogen Peroxide Production Can Reduce Microbial Load in Bioponic Nutrient Solutions Derived from Organic Waste

Technological advancement in recent decades has allowed for crop cultivation in soilless controlled environments, known as hydroponics, and this is being employed in an increasing number of factories worldwide. With continued local and regional disruptions in the supply chain to provide mineral fertilizers, new pathways to generate nutrient solutions are being developed. One potential approach is the recovery of nutrients from organic waste and wastewater using bioponics. Bioponics refers to the biological mineralization of organic residues through processes such as anaerobic and aerobic digestion and the use of such organically produced nutrient solutions in hydroponic systems. However, without disinfection of the nutrient solution, the high microbial loads increase the risk of pathogens affecting plant and consumer health. In this work, electrochemical hydrogen peroxide (H2O2) demonstrated success in reducing microbial loads. Different scenarios of application were considered: (1) variation in the H2O2 concentration in the nutrient solution by dosing H2O2 from ex situ electrochemical production, (2) variation in the dosing time-dependent reaction between the nutrient solution and H2O2 produced ex situ, and (3) the in situ production of H2O2 of the organic nutrient solution. The highest tested H2O2 concentration of 200 mg L−1 showed a microbial load reduction of bacteria at 93.3% and of fungi at 81.2%. However, the in situ production showed the highest reduction rate for bacteria and fungi in bioponic nutrient solutions, where longer reaction times also impact microbial concentrations in situ. Final microbial reductions of 97.8% for bacteria and of 99.1% for fungi were determined after a H2O2 production time of 60 min. Overall, our results show that electrochemical H2O2 production can be used to disinfect bioponic nutrient solutions, and the production cell can be implemented in bioponic systems in situ.

Dissolved organic matter and nutrient processing in organic-rich subterranean estuaries: Implications for future land use and climate scenarios

The subterranean estuary (STE) is a recognized reactive biogeochemical zone at the groundwater–seawater interface in coastal regions. However, few studies have explored dissolved organic matter (DOM) and nutrient processes in buried organic-rich STEs (with up to 20 % of organic matter content), despite their potential contributions to coastal water hypoxia and greenhouse gas emissions. This study conducted controlled laboratory experiments to investigate the physicochemical controls on DOM and nutrient processing in organic-rich STEs, considering variations in groundwater nitrate (NO3–) concentrations, salt concentration, seawater ions, and incubation times. Results showed elevated levels of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in pore water, primarily from particulate organic matter (POM) degradation that originated from decayed vascular plants. POM-to-DOM degradations further resulted in the accumulation of ammonium (NH4+) and highly unsaturated compounds in all treatments. The addition of high-ionic-strength treatments (e.g., seawater and sodium chloride [NaCl] solution) reduced DOC solubility and selectively removed dissolved aromatic compounds in porewater. The cation-rich seawater shifted the porewater NH4+ generation pathway from predominantly biological (re)mineralization in freshwater to abiotic (desorption via ion exchange) pathways in the saline water setup. Orthophosphate (PO43−) dynamics were likely to be influenced by the iron-rich sediment surface in both freshwater and saline water scenarios. Our experiments further indicated that the long-term incubation enriched DOM concentration with a high degradation state. This work demonstrated that organic-rich STEs are significant sources of less labile DOM and NH4+ to coastal waters. In the context of global climate change, our results illustrate the sensitivity of DOM and nutrient biogeochemical cycling in STEs to salinization and altered residence time, consequently affecting the quantity and quality of DOM and nutrients transported to coastal waters.

Iron bound phosphorus predominates the contribution of phosphorus to lake system from terrigenous source: The evidence from the small watershed scale

The reduction of exogenous emissions of phosphorus (P) is a crucial measure for resolving eutrophication in lakes. However, the input of terrigenous materials still potentially contributes to an increase of P load in lake systems. In this study, we examined the phosphate oxygen isotope (δ18OP) of various P fractions in soils and sediments in a small lake watershed, namely, Shijiuhu watershed. The high-resolution in-situ diffusive gradients in thin films (DGT) technology was also used to survey the dynamic processes of P diffusion from sediment particles to the water. The results demonstrated that lighter δ18OP values (16.2–19.5‰) for individual P fractions in lake sediments were detected compared to other land-use patterns, indicating the cumulative biological P recycling on anaerobic condition. Fe bound P (Fe-P) overall had heavier δ18OP values (17.3–24.8‰) than some of Ca bound P (Ca-P) and equilibrium values, suggesting that Fe-P conserved the parental isotope signatures from terrigenous source and could act as the ideal tracer for the lake sediments. The mixing effect of terrigenous detrital input and biological mineralization made the source identification uncertain by using Ca-P, which had a wider range of δ18OP values (13.0–26.6‰). Additionally, significantly positive correlation (r = 0.551–0.913, p<0.05) between soluble reactive P (SRP) and Fe2+ in interstitial water obtained using DGT measurement revealed the conspicuous release and desorption of solid Fe-P toward the water. High diffusion fluxes from the sediments toward the overlying water further demonstrated that the desorption of Fe-P in the soil-originated sediments toward the solution conspicuously facilitated the accumulation of SRP in lake water. The first-time application of δ18OP isotope combined with in-situ DGT techniques certified that it's feasible for the contribution confirmation from terrigenous to lacustrine environments, and presented the direct evidence for management strategy making about P control and eutrophication restoration at the catchment scale of lakes.

Successful non-surgical endodontic management of type III dens invaginatus by using cone-beam computed tomography: a case report

Dens invaginatus (DI) is a rare malformation of a tooth caused by the invagination of tooth crown before biological mineralization occurs. In DI type III invagination extends beyond the cementum-enamel junction, with the second foramen extending into the periapical tissues or into the periapical area. DI type III may pose real challenges for the clinician, especially when endodontic treatment is required. Objective: The present case report describes the successful non-surgical endodontic management of a tooth with DI type III with the aid of cone-beam computed tomography (CBCT). Case report: A 20-year-old male patient was referred for endodontic evaluation and treatment of the left maxillary lateral incisor (tooth #22), which presented a darker and unusual crown shape. Periapical radiography and CBCT scans revealed the presence of a type III DI, and a larger periapical lesion associated with external root resorption and discontinuous buccal cortical plate Results: The diagnosis of Oehlers type III DI with asymptomatic apical periodontitis was established, and non-surgical endodontic treatment was initiated. After 5 months, a decrease in the periapical lesion and arrest of external resorption was detected. The root canals were then filled, and the tooth restored. At the 3-years follow-up, clinical and imaging assessments revealed successful outcome of the treatment. Conclusion: CBCT is an inestimable tool for non-surgical endodontic management of teeth with complex internal anatomy, such as DI type III with associated large periapical lesion.

Sustainable Phenylalanine-Derived SAILs for Solubilization of Polycyclic Aromatic Hydrocarbons.

The solubilization capacity of a series of sustainable phenylalanine-derived surface-active ionic liquids (SAILs) was evaluated towards polycyclic aromatic hydrocarbons-naphthalene, anthracene and pyrene. The key physico-chemical parameters of the studied systems (critical micelle concentration, spectral properties, solubilization parameters) were determined, analyzed and compared with conventional cationic surfactant, CTABr. For all studied PAH solubilization capacity increases with extension of alkyl chain length of PyPheOCn SAILs reaching the values comparable to CTABr for SAILs with n = 10-12. A remarkable advantage of the phenylalanine-derived SAILs PyPheOCn and PyPheNHCn is a possibility to cleave enzymatically ester and/or amide bonds under mild conditions, to separate polycyclic aromatic hydrocarbons in situ. A series of immobilized enzymes was tested to determine the most suitable candidates for tunable decomposition of SAILs. The decomposition pathway could be adjusted depending on the choice of the enzyme system, reaction conditions, and selection of SAILs type. The evaluated systems can provide selective cleavage of the ester and amide bond and help to choose the optimal decomposition method of SAILs for enzymatic recycling of SAILs transformation products or as a pretreatment towards biological mineralization. The concept of a possible practical application of studied systems for PAHs solubilization/separation was also discussed focusing on sustainability and a green chemistry approach.

Chemical characterization and biological properties of titania/hydroxyapatite-promoted biomimetic alginate-chitosan-gelatin composite hydrogels

Ceramic nanoparticles, hydroxyapatite (HAP) and titania (TiO2) nanoparticles were commonly used as the reinforcing agent for biological materials due to their high chemical stability, low toxicity, outstanding biocompatibility and good bioactivity, which will be beneficial to enhance the physical, chemical and biological properties of composite hydrogels. To fundamentally improve the bio-applicability of alginate hydrogels, we attempted to fabricate titania/hydroxyapatite-promoted biomimetic alginate-chitosan-gelatin (Alg/TiO2/HAP-CS-GT) composite hydrogels by physical blending method using HAP nanoparticles as both the reinforcing agent and the endogenous cross-linking agent, followed by surface modification through alternately electrostatic assembly of chitosan (CS) and gelatin (GT). Meanwhile, the effects of the addition of TiO2 nanoparticles on the pore structure, mechanical properties, swelling, biodegradability, biological mineralization ability and biological activity of Alg/TiO2/HAP-CS-GT composite hydrogels were mainly studied. Experimental results showed that the resultant Alg/TiO2/HAP-CS-GT composite hydrogels exhibited good 3D morphology with the porosity in the range of 86.90%–77.62% and pore size ranging from 210 μm to 90 μm. Moreover, the compressive strength and modulus of Alg/TiO2/HAP-CS-GT composite hydrogels were significantly improved with increasing of TiO2 nanoparticles content and reached up to 0.329 ± 0.012 MPa and 0.558 ± 0.035 MPa, respectively. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetric analyses (TGA) implied that the interfacial interaction between TiO2 nanoparticles and polymer in Alg/TiO2/HAP-CS-GT composite hydrogels was inferred to be the hydrogen bond interaction. Furthermore, the addition of TiO2 nanoparticles could effectively regulate the swelling, in vitro biodegradation and biomineralization, and biological activity of the composite hydrogels. In particular, Alg/TiO2/HAP-CS-GT composite hydrogels could exhibit good cell adhesion and cell proliferation activity. When the addition amount of TiO2 nanoparticles was 1.0% (w/v), Alg/TiO2/HAP-CS-GT composite hydrogels exhibited the highest cell proliferation activity. In addition, with increasing of TiO2 content, the relative alkaline phosphatase (ALP) activity of cells on the Alg/TiO2/HAP-CS-GT composite hydrogels gradually increased, indicating that the addition of TiO2 nanoparticles could also effectively promote cell differentiation. On account of these excellent physical, chemical and biological activities of Alg/TiO2/HAP-CS-GT composite hydrogels, they were expected to be applied in the field of tissue engineering.

Biomimetic mineralization of calcium carbonate under synergistic regulation of Sr2+ and egg-white proteins

The content of Sr in nacre is stable and second only to Mg, but its ability to induce aragonite is rarely reported. Therefore, the paper studied the effects of Sr2+ concentration, reaction rate and temperature on the biological mineralization of calcium carbonate in presence of egg-white proteins. The results show that Sr2+ could induce the formation of aragonite when coexisting with egg-white proteins as Mg2+. However, the large ion radius of Sr2+ makes it difficult to enter the calcite lattice, so its induction efficiency is much lower than Mg2+. Reducing the mineralization rate and increasing the mineralization temperature are beneficial to the formation of aragonite.

Outer fold is sole effective tissue among three mantle folds with regard to oyster shell colour

Molluscs constitute the second largest phylum of animals in the world, and shell colour is one of their most important phenotypic characteristics. In this study, we found among three folds on the mantle edge of oyster, only the outer fold had the same colour as the shell. Transcriptome and mantle cutting experiment indicated that the outer fold may be mainly reflected in chitin framework formation and biomineralisation. There were obvious differences in SEM structure and protein composition between the black and white shell periostraca. The black shell periostraca had more proteins related to melanin biosynthesis and chitin binding. Additionally, we identified an uncharacterized protein gene (named as CgCBP) ultra-highly expressed only in the black outer fold and confirmed its function of chitin-binding and CaCO3 precipitation promoting. RNAi also indicated that CgCBP knockdown could change the structure of shell periostracum and reduce shell pigmentation. All these results suggest that the mantle outer fold plays multiple key roles in shell periostraca bioprocessing, and shell periostracum structure affected by chitin-binding protein is functionally correlated with shell pigmentation. The investigation of oyster shell periostracum structure and shell colour will provide a better understanding in pigmentation during biological mineralisation in molluscs.

Microbe‐Mediated Biosynthesis of Multidimensional Carbon‐Based Materials for Energy Storage Applications

AbstractBiosynthesis methods are considered to be a promising technology for engineering new carbon‐based materials or redesigning the existing ones for specific purposes with the aid of synthetic biology. Lots of biosynthetic processes including metabolism, fermentation, biological mineralization, and gene editing have been adopted to prepare novel carbon‐based materials with exceptional properties that cannot be realized by traditional chemical methods, because microbes evolved to possess special abilities to modulate components/structure of materials. In this review, the recent development on carbon‐based materials prepared via different biosynthesis methods and various microbe factories (such as bacteria, yeasts, fungus, viruses, proteins) are systematically reviewed. The types of biotechniques and the corresponding mechanisms for the synthesis of carbon‐based materials are outlined. This review also focuses on the structural design and compositional engineering of carbon‐based nanostructures (e.g., metals, semiconductors, metal oxides, metal sulfides, phosphates, Mxenes) derived from biotechnology and their applications in electrochemical energy storage devices. Moreover, the relationship of the architecture–composition–electrochemical behavior and performance enhancement mechanism is also deeply discussed and analyzed. Finally, the development perspectives and challenges on the biosynthetic carbons are proposed and may pave a new avenue for rational design of advanced materials for the low‐carbon economy.

Facet Dependence of Biosynthesis of Vivianite from Iron Oxides by Geobacter sulfurreducens.

Vivianite plays an important role in alleviating the phosphorus crisis and phosphorus pollution. The dissimilatory iron reduction has been found to trigger the biosynthesis of vivianite in soil environments, but the mechanism behind this remains largely unexplored. Herein, by regulating the crystal surfaces of iron oxides, we explored the influence of different crystal surface structures on the synthesis of vivianite driven by microbial dissimilatory iron reduction. The results showed that different crystal faces significantly affect the reduction and dissolution of iron oxides by microorganisms and the subsequent formation of vivianite. In general, goethite is more easily reduced by Geobacter sulfurreducens than hematite. Compared with Hem_{100} and Goe_L{110}, Hem_{001} and Goe_H{110} have higher initial reduction rates (approximately 2.25 and 1.5 times, respectively) and final Fe(II) content (approximately 1.56 and 1.20 times, respectively). In addition, in the presence of sufficient PO43-, Fe(II) combined to produce phosphorus crystal products. The final phosphorus recoveries of Hem_{001} and Goe_H{110} systems were about 5.2 and 13.6%, which were 1.3 and 1.6 times of those of Hem_{100} and Goe_L{110}, respectively. Material characterization analyses indicated that these phosphorous crystal products are vivianite and that different iron oxide crystal surfaces significantly affected the size of the vivianite crystals. This study demonstrates that different crystal faces can affect the biological reduction dissolution of iron oxides and the secondary biological mineralization process driven by dissimilatory iron reduction.

369Fabrication of 3D gel-printed β-tricalcium phosphate/titanium dioxide porous scaffolds for cancellous bone tissue engineering.

Human bone is composed of cortical bone and cancellous bone. The interior portion of natural bone is cancellous with a porosity of 50%-90%, but the outer layer is made of dense cortical bone, of which porosity was not higher than 10%. Porous ceramics were expected to be research hotspot in bone tissue engineering by virtue of their similarity to the mineral constituent and physiological structure of human bone. However, it is challenging to utilize conventional manufacturing methods to fabricate porous structures with precise shapes and pore sizes. Three-dimensional (3D) printing of ceramics is currently the latest research trend because it has many advantages in the fabrication of porous scaffolds, which can meet the requirements of cancellous bone strength, arbitrarily complex shapes, and individualized design. In this study, β-tricalcium phosphate (β-TCP)/titanium dioxide (TiO2) porous ceramics scaffolds were fabricated by 3D gel-printing sintering for the first time. The chemical constituent, microstructure, and mechanical properties of the 3D-printed scaffolds were characterized. After sintering, a uniform porous structure with appropriate porosity and pore sizes was observed. Besides, biological mineralization activity and biocompatibility were evaluated by in vitro cell assay. The results demonstrated that the incorporation of TiO2 (5 wt%) significantly improved the compressive strength of the scaffolds, with an increase of 283%. Additionally, the in vitro results showed that the β-TCP/TiO2 scaffold had no toxicity. Meanwhile, the adhesion and proliferation of MC3T3-E1 cells on scaffolds were desirable, revealing that the β-TCP/TiO2 scaffolds can be used as a promising candidate for repair scaffolding in orthopedics and traumatology.

The roles of heteromorphic crystals and organic compounds in the formation of the submandibular stones

ObjectiveThe study aimed to analyze the formation process of submandibular stones based on the theory of biological mineralization and inorganic crystal structure variation. Study designFrom January 2021 to December 2021, patients with submandibular stones treated in the Affiliated Hospital of Stomatology, Sun Yat-sen University (Guangzhou, China) were selected. According to the criterion of maximum transverse diameter ≥3 mm, a total of five submandibular stones meeting the requirement were included. After the surface of sample stones were washed, they were cut along the maximum transverse diameter. Next, the study employed Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and polycrystalline X-ray Diffraction (XRD) to analyze the composition and structure of submandibular stones. ResultsFive submandibular stones were included. The organic and inorganic compounds showed a rhythmic or irregular distribution. Submandibular stones were highly occupied with carbon (C), oxygen (O), calcium (Ca), and phosphorus (P). Hydroxyapatite (HAP) was the primary inorganic component. In addition, the precursor of HAP, namely Amorphous Calcium Phosphate (ACP), was also found. Tetrahedral Substitution Index (TSI) and Ca/P ratio reflected the degree of structural variation in HAP crystal, which fluctuated from 5.62-90.71 and 1.10–1.35, respectively. ConclusionsThe development of submandibular stones was influenced by inorganic crystals’ chemical and structural variation as well as the organics’ regulation towards the inorganic. The isomorphic substitution was accompanied by the occurrence of inorganic crystals, resulting in the crystal structure change. Organics might influence the appearance, aggregation, and mineralization of HAP during its formation.